


Some Concepts Are Better Understood Naked

by Just_Breezy



Series: Math is Fundamental [3]
Category: Supernatural
Genre: Alternate Universe, Alternate Universe - High School, Anal Plug, Anal Sex, BDSM, Butt Plugs, Castiel Talks Dirty, Dirty Talk, Dom!Cas, Dom/sub, Fluff and Smut, M/M, Math Kink, Maths (sorry), Orgasm Delay/Denial, PWP, PWP without Porn, Plot What Plot, Porn Without Plot, Romance (Kind of), Shameless Smut, Smut, Spanking, Student!Dean, Sub!Dean, Top!Cas, Underaged!Dean, Vibrators, alternate universe - AU, bottom!Dean, teacher!Cas
Language: English
Status: Completed
Published: 2014-10-04
Updated: 2014-10-04
Packaged: 2018-02-19 19:46:45
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 2,963
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2400692
Author URL: https://archiveofourown.org/users/Just_Breezy/pseuds/Just_Breezy
Summary: <blockquote class="userstuff">
              <p>With Dean's new relationship with his calculus teacher, his grades have been slipping, and without any explanation, Bobby and Ellen did what any (albeit surrogate) parents would do: ask Mr. Novak to give Dean one-on-one tutoring sessions.</p>
            </blockquote>





	Some Concepts Are Better Understood Naked

**Author's Note:**

> So, if you've been reading the 'series', I'm sure you've picked up on the fact that I may have a certain... affinity to math, but I loathe logarithms and was going to skip over this unit. However, we're running out of units to cover before Dean graduates, so I'm sorry if there are any problems with the actual math
> 
> Also, as ever, you don't *need* to read the series to appreciate this, or any of the fics in the 'series', they're all good as simple porn.
> 
> Personally, I still prefer Illegal to this, but you know the deal, enjoy the smut!
> 
>  
> 
> OH! Be warned: There's romance at the end of the fic, it's grossly sweet and slightly OOC.

    There are many things that come naturally to Dean, but even he need to pay attention in calculus. Which he hasn't. With his grades starting to slip and neither Bobby or Ellen could understand why. So they did what any concerned (albeit surrogate) parents would do: ask Mr. Novak to give Dean private tutoring sessions; and Mr. Novak being the benevolent and worried teacher he is, agreed.

    As anticipated (by Dean), the sessions have gone from very informative and productive to this:  
Dean sat in the cool chair, occasionally losing focus on the matters at hand to address how cold the plastic felt against his naked body, or how the cuff linking him to the chair/desk rattled as hr wrote down notes, trying to keep up with the information. The real deterrent being Castiel himself, or rather the fact that all he was wearing was an intricate set of leather straps reaching over his shoulders, waist and down to his throbbing cock, all meeting in a ring just above his navel. The guy could keep a boner even when 'teaching' math, and though impressive, very distracting.

    "Mr. Winchester, I don't believe the problem will solve itself." Dean focused on the board, finally averting his eyes from Castiel's firm leather-clad form. The question read 'Find the derivative of f(x) = log5(xex)'. Thankfully, Dean wasn't paying attention, or really understood how to differentiate logarithms.

    Of course, if Dean told Mr. Novak that he wasn't paying attention, the punishment would be far worse than simply getting the question wrong. As he was writing out a completely guesswork answer, Mr. Novak became impatient, "hurry up Mr. Winchester, we have a lot to cover." Dean scribbled down the last of his answer and raised his hand to signal his completion.

      
    "And the answer is?"  
    "xexln(5), sir."

  
    Dean spasmed violently while breathy moans coated his lips as Mr. Novak switched the vibrating plug from 0 to 3. Dean had long since adjusted to the feeling of it, but every time he got a question wrong, Castiel would make it vibrate viciously, sending his student into a rapture of pleasure and shock. Castiel gave Dean three minutes of the vibrator on it's highest setting before finally turning it off. Dean felt entirely shaken and raw from the overstimulation, but wickedly turned on and desperately unsatisfied. Castiel had been getting creative with his punishments for his petulant student; it seemed sexual stimulation worked better than simple force.

    "Tell me, boy, where do you think you went wrong?" His student shivered, knowing if he got this question wrong, Mr. Novak wouldn't hold back on the controls. If anything, he enjoyed it more when Dean got questions wrong. "Um, maybe-" his words were consumed by a shuddering moan as Castiel twisted the dial. "We've talked about indecisiveness, Dean. You cannot  _think_ the answer _might_ be right, either it is or it isn't, there is no in between." The older man's smoky voice affected Dean more than the vibrating plastic against his prostate. No matter what Castiel was saying, it always turned Dean on, especially when he was reprimanding Dean, or praising him.

    The boy continued to writhe in his chair while Castiel mercilessly carried on the onslaught, "I'll ask you again, slut, where do you think you went wrong?" Castiel leaned against his desk at the front of the class casually, while Dean wantonly mewled in a desk in the second row, blue chair warming up under him as his body heated up, blush painting his freckled skin.

    "Wh-when I applied the- natural logarithm rule," Dean moaned around every word, barely able to get the sentence out. Castiel cocked his eyebrow, seeing Dean would be nearing his orgasm at the rate he was being stimulated. Castiel's own erection desperately ignored and heavy between his legs. Deciding the only appropriate punishment for Dean's blatant distrait behavior, Castiel chose to enjoy the show and wait until his student was on the verge of release.

    The boy's eyes rolled back into his head while the continued vibration became less overstimulating and more pleasurable as Mr. Novak turned the dial down to a much better setting, his teacher stroking his cock at the beautiful sight of his little slut melting into the touch of impersonal plastic. "You're so desperate to have your ass nice and full, you would come from a plastic plug shoved up your ass, you don't even care what it is, as long as it fills you up," Castiel noted mostly to himself, as Dean was preoccupied with getting very close to coming, canting his hips on the chair. "Go ahead, pet, you can touch yourself," Mr. Novak murmured just loud enough for Dean to hear. His shoulders relaxed as his hand found his dreadfully neglected cock, his teacher quietly moaning with the boy; "that's it, just enjoy it," Castiel continued to coo.

    Dean was in complete bliss an so very very close. Hs mouth went slack as he felt the familiar coil in his stomach about to release- then nothing! Mr. Novak turned the plug off, jolting his student out of his nirvana. "You may remove your hand from your cock, Mr. Winchester, we have a question to work through." Dean's eyes flashed open, shock and indignation evident within the brilliant green of his eyes, jaw hanging open for completely different reasons now. Castiel grinned sinfully watching Dean's stunned face while his hand instinctively flew off his dick; Castiel was certainly doing a fantastic job of making his perfect slut the perfect sub. Dean searched his teacher's face for any indication of why he wasn't allowed to come, or why he was given so much indulgence only to have it taken away so quickly, but found only sadistic satisfaction. Mr. Novak nonchalantly stroked his cock with one hand while writing on the board with the other, clearly relishing in his student's discontent. Castiel love his pet's face in ecstasy, but only when _he_ was the cause, otherwise it was much more gratifying to watch him be left unsatisfied, the best punishment.

    "So, as we can see, the answer is f'(x) = (x+1)/xln(5)." Castiel turned around to his student frantically writing down the equatoin, still flushed from the almost-orgasm. Mr. Novak walked to Dean's desk, smiling lasciviously, and knelt beside his young student, "my poor student," Castiel began to run his hands up Dean's thighs, tracing patterns into the sensitive skin, "you're working so hard," Castiel began kissing his chest, stopping to suck and bite at his student's nipples, "and I don't even let you come." Castiel's hands began a torturously slow pace on Dean's hard on, while his mouth continued to explore his chest and neck, occasionally the leather he wore rubbed against his student's responsive body, causing Dean to shudder and moan. Castiel continued to hum words of praise into his pliant student's neck, reverberating throughout Dean's body, setting every nerve on fire; he loved and hated the excruciating drag of leisurely  pleasure, but he also knew that was the intention, and that seemed to make it all the more better and painful.

    "Can my favorite slut answer one simple question?" Castiel purred. "Of course, sir." The older man smiled, remembering the dauntless boy he began with, now so very obedient. "Can my beautiful pet tell me the derivative of ecot^-1 (x^2) \+ x3?" Castiel turned the plug on low as Dean began to work, only momentarily distracting the boy. Dean shifted lightly as Castiel began kissing from his knee moving upward, "I can't decide what I love more: your face when working through a problem, or your face right before coming. You are truly beautiful, Dean." The last of the sentence was said around the head of Dean's cock; the boy's mouth formed a perfect 'O', delicate lips parting in undiluted bliss, while his eyes remained completely focused on the task at hand. Castiel smirked and the dial up, hoping to break his young student. Dean stopped and enjoyed the delicious stimulation, even if it drove him mad, needing to come, like yesterday. He continued his work, hand unconsciously moving to his dick as his not-so-benevolent teacher removed his mouth. This earned him a harsh slap, "I'm disappointed, Mr. Winchester, there aren't many rules, and yet you still seem to struggle." Dean looked wide-eyed at Castiel, completely haulting his work, "please sir-" he began. "Finish the question, then we shall discuss appropriate actions."

    Dean finished the question hastily, raising his hand again. 

  
    "And the answer is?"  
    "f'(x) = ecot^-1 (x^2) [- (1/(x2)2\+ 1) (2x)] + 3x2], sir."  
    "Excellent work, pet. You've been very good, but you've also broken a rule, and you know what that means, and for that I believe an indefinite number of spanks is appropriate, while for all your hard work, you can request one thing. Does that seem fair, slut?"  
    "Thank you, sir! I- yes, that seems fair... can you- _please_ fuck me? This plug isn't you, and I just-! Please let me come on your cock, sir!"

  
    Castiel smiled, god, Dean was a cockslut and especially needy after a long tutoring session, and endlessly gorgeous when desperately trying to satisfy himself without having any contact, (beyond the relentless vibrating plug). "Very well then, Mr. Winchester. Lets begin with the spanking." Dean intuitively got up from his seat, and though he was cuffed to the arm, manoeuvred his way around it until his pert ass writhed in the air, on display and waiting, the black plug sharply contrasting his pale skin.

    Mr. Novak walked behind the boy, erection gently teasing his thigh as the older man leaned over to whisper into the boy's ear, "I'm not going to be gentle." With that, Dean trembled with exhilaration as Mr. Novak's hand made harsh contact with the boy's ass. Both of them winced with enjoyment for very different reasons. Four more slaps followed in quick succession. Each time Castiel's hand made contact, the older man would turn the dial up slightly, ensuring every now and then his hits touched the teen's sensitive rim, enhancing both the pain and pleasure equally. Castiel hit harder, keeping true to his word, ensuring Dean was a hot mess, writhing and wordlessly begging on the impersonal desk. Castiel loved watching Dean react so eagerly, especially while submitting so wholly to the punishment. "Do you think you've been scolded enough, pet?" The older man rubbed affable patterns over the smatterings of forming handprints, humming quietly while Dean collected his thoughts. "N-no, sir." His teacher raised an eyebrow as Dean canted his hips towards the older man. "Why's that, Mr. Winchester?" Dean's legs trembled, threatening to give out, matching the fluttering of his voice, "I sho-should know better by now than to br-break a rule."

    Evidently, Dean was quickly becoming the perfect sub, only making Castiel love him more, "very well then." Castiel continued to revile the teen's reddening ass until he felt the boy could not take any more. The teen panted while his teacher knelt between his lissome student's overworked legs, kissing the ridges of forming welts. "Now, lets get this thing out of you," Castiel lulled, fingers pressing against the sensile ring of muscle holding in the black vibrator. The student gasped as Castiel pulled the plug out forcibly. With the plug gone, Dean mewled at the emptiness. Castiel kissed the boy's ass before standing up and patting him on the back, "turn around and sit on the desk, slut," Castiel commanded.

    Without wasting a moment, Dean stood up and shuffled awkwardly, right wrist still cuffed to the arm, until he was sitting on the desk, facing Mr. Novak, hands begging to hold onto his master's leather straps, while his legs instinctively opened wider. Castiel reached under Dean's seat, grabbing the lube from his student's pants, and began rubbing some of the cool liquid over his aching cock, watching Dean shift excitedly on the desk, waiting.

    The older man grabbed the student's legs from behind his knees. Dean leaned back, looking for any indication of what to do next, anticipation building. Their tutoring session had been going on for almost two hours, and  _finally_ , there would be glorious relief. Dean's legs rested on the black leather straps covering Castiel's shoulders, giving his calfs a perfect bite of leather.

    Castiel pushed in unceremoniously into the lithe teen, pressing the hard leather over his perineum, relentlessly exploiting the teen's overstimulated prostate on the first thrust. The older man savoured the delicious sounds coming from his student. Setting up a ruthless pace, Castiel fucked Dean for all his worth, fragile legs shaking on his shoulders, exquisite moans a continuos mantra. With every astringent thrust, Dean was treated to a strdent slap of leather as well, making the pain and pleasure that much more consuming.

      
    "Are you owned!?"  
    "Yes-!"  
    "Are you my bitch, Dean!?"  
    "Oh god,  _yes_ , I'm your- your-!"  
  


    Castiel stalled his movements, still completely buried within Dean, "tell me, boy, will you ever be able to fuck another man?" Dean tried to thrust himself on Castiel's dick to no avail. "N-no, please sir,  _fuck_ -!" The older man smiled, "then why aren;t you coming?" With that, Dean let go without even realizing he was holding back, screaming, his body moved of it's own accord, writhing on the desk. Castiel began fucking Dean through his orgasm, not lasting long as the boy tightened around his cock, throbbing over the length.

    Dean's legs went lax and slid off his teacher's shoulders, completely spent. Castiel slipped out the teen and grabbed some tissue from the dispenser by the door along with the keys to the cuffs.

    The boy watched as his teacher wiped up his slack abdomen and undid the cuff from his wrist. Castiel moved to his plush chair at the front of the room, motioning for Dean to come, "aren't you going to join me?" Unwilling to move, Dean got up, crawling onto the older man's lap, face snug against his neck, legs falling off the side of the chair. Castiel hummed in satisfied ease as he rubbed Dean's muscled back, dropping kisses to his student's head every now and again.

      
    "Dean, I have to ask, as your teacher, did you actually learn anything today?"  
    "Of course. I learned that you need to wear this way more often, quite possibly under your ridiculous sweater vests."  
  


    Castiel frowned and lightly smacked Dean's shoulder, "I'm serious, should I look into tutoring options?" Dean sighed, he really didn't want to be taught math by anyone but Castiel; "maybe I'll try actually paying attention in class before we start looking at tutors." Castiel settled back into the cuddle, teaching duty done, loving the warmth of Dean's skin against his, though he could still feel his student was not as relaxed.

    "What's wrong, Dean?" The boy entirely locked up before forcing himself to be completely lax; "nothing's wrong..." Castiel frowned again and pulled away slightly to look at Dean better, "seriously, what's on your mind?"

    Dean shifted uncomfortably before standing up and walking back to his desk, where his clothes were. The boy tried to hide how red his face was, a mix of emotions contorted his graceful features. Castiel watched, nervous with what was to follow. The boy dug through his pants before returning to his teacher's lap, hands clasped around something, sending Castiel's heart rate through the roof. "Dean, please tell me that's not-" The boy opened his hands, presenting a small black velvet box.

    "No, shut up. This is... god, this is so lame... I hope... I hope you appreciate that I'm breaking my 'no chick flick moments' rule. Fuck, alright, Cas, first of all, this is not an engagement ring... this is my promise to you that... fuck, I'm sorry, this is all new to me... but I know our whole relationship is fucked up, but I want to make this work, I want this to last, because... well, fuck, you just, you make me so happy, and... I don't want that to end anytime soon."

    Dean stared at the box the whole time, unwilling to see the possible mockery in Castiel's face, before opening the small box to reveal a thin, simple silver ring. Castiel couldn't breathe, face showing the apparent awe. The teen finally looked up to see Castiel staring back at him, both lost for words.

    Dean began to panic as Castiel didn't immediately respond, when finally, as Dean began to pull away in horror, the older man wrapped his arms around him and kissed him passionately, pushing the tears of happiness back. He _was not_ going to cry that his student, his  _boyfriend_ felt just as strongly about him as he did.

    The teen pulled away from the kiss, gasping for air, finally breaking into laughter (and secretly extreme relief).

  
    "So, I'll take that as a 'you accept'?"  
    "Of course, you assbutt."  
    "'Assbutt'? Really?"  
    "I'm sorry I'm not as articulate as you, Mr. _I-know-our-whole-relationship-is-fucked-up_."

  
    They both laughed and Dean slipped the ring onto Castiel's right ring finger (as much as he wanted Cas to wear it liked a wedding band, that would be far too suspicious for a single teacher), kissing the digit once it was on. Both men admired it, fitting perfectly on Castiel's finger. "I love it, Dean, I love you... but next time you mysteriously pull out a velvet box, there better be a diamond ring in there."

    Dean and Castiel laughed and breathed in the air of love and the perfectly awkward and un-serious expression of love. Somehow, if it wasn't weird, uncoordinated and bordering on hilarious, it wouldn't be them... and neither of them would have it any other way... 


End file.
